# Fileset

[supporting information-no highlight-1.docx](https://mdr.nims.go.jp/filesets/c4cb059a-b18e-4c04-bcc5-be9b1974920f/download)

## Creator

Yunfei Gao, [Mukesh Kumar](https://orcid.org/0000-0001-8841-5080), [Neha Thakur](https://orcid.org/0000-0002-1376-1250), [Weijie Cao](https://orcid.org/0000-0003-0033-1857), [Toshiki Watanabe](https://orcid.org/0000-0003-1798-1987), [Satoshi Tominaka](https://orcid.org/0000-0001-6474-8665), Kazutaka Sonobe, Akihiko Machida, Ryota Sato, [Toshiharu Teranishi](https://orcid.org/0000-0002-5818-8865), Masashi Matsumoto, [Hideto Imai](https://orcid.org/0000-0002-9434-1492), Tomoya Uruga, Yoshiharu Sakurai, [Yoshiharu Uchimoto](https://orcid.org/0000-0002-1491-2647)

## Rights

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright © 2025 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsami.5c03118.[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[Structure–Activity Relationship in PtCo L10 Ordered Phase ORR Catalysts: Pt-Rich Shell Having Anisotropic Lattice Distortion Revealed by PDF and XAS Analysis](https://mdr.nims.go.jp/datasets/419797b7-d4bb-4300-9387-92aca4912140)

## Fulltext

Supporting InformationStructure-Activity Relationship in PtCo L10 Ordered Phase ORR Catalysts: Pt-rich Shell having Anisotropic Lattice Distortion Revealed by PDF and XAS AnalysisYunfei Gao1†, Mukesh Kumar1†*, Neha Thakur1, Weijie Cao1, Toshiki Watanabe1, Satoshi Tominaka2†*, Kazutaka Sonobe2, Akihiko Machida3, Ryota Sato4, Toshiharu Teranishi4, Masashi Matsumoto5, Hideto Imai5, Tomoya Uruga6, Yoshiharu Sakurai6, Yoshiharu Uchimoto11 Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan2 Center for Basic Research on Materials, National Institute for Materials Science, Namiki, Tsukuba, Ibaraki 305-0044, Japan3 Synchrotron Radiation Research Center, National Institutes for Quantum Science and Technology (QST), SPring-8, Sayo, Hyogo 679-5148, Japan4 Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan5 Fuel Cell Cutting-Edge Research Center Technology Research Association, Aomi, Koto, Tokyo, 135-0064 Japan6 Japan Synchrotron Radiation Research Institute (JASRI), Koto, Sayo, Hyogo, 679-5198, Japan*Corresponding authors: kumar.mukesh.5x@kyoto-u.ac.jp, TOMINAKA.Satoshi@nims.go.jp† Authors contributed equally to this workFigure S1 XRD patterns of PtCo alloys (a) treated at different thermal temperatures and (b) different thermal treatment times, (c) XRD of  PtCo alloys at 250 and 300 °C. Black lines represent the standard reference for fct L10 PtCo JCPDS: 65-8969.Figure S2 Crystallite size of PtCo catalysts as a function of annealing temperature. The crystallite size was estimated from the 111 reflections in the XRD patterns using the Scherrer equation.Figure S3. Pt L3-edge XANES spectra of the catalysts treated for different times at (a) 450 °C and (d) 600 °C.Figure S4. The Co K-edge XANES spectra of the catalysts treated for different times at (a) 450 °C and (b) 600 °C.Figure S5. EXAFS fitting details for the Pt L3-edge for (a) PtCo-350°C-10h-A and (b) PtCo-700°C-10h-A. EXAFS fitting details for the Co K-edge for (c) PtCo-350°C-10h-A and (d) PtCo-700°C-10h-A.The r space data was used to fit with the application of k3 weighting over the ranges 3.0 ≤ k ≤ 16.0 and 1.5 ≤ r ≤ 3.3 for the Pt L3-edge. For the Co K-edge, fits were undergone in R-space for 1.4 ≤ r ≤ 3.1 Å, and the k,3 weighting over the ranges 3.0 ≤ k ≤ 12.0. During the fitting, the following constraints were introduced: 12 Where  () is the bond length for the Pt-Co (Co-Pt) scattering, the total coordination number for the Co () is assumed to be 12 for the FCC and FCT structure (only the bulk phase Co is considered in the catalysts). Figure S6 Rietveld refinement and PDF fitting results for PtCo catalysts annealed at different temperatures for 2 hours followed by acid treatment. (top) Total scattering patterns refined by the Rietveld method. Each partial contribution of the phases determined in Figure 4 of the main text, along with their hkl indices shown as vertical ticks, are displayed. (bottom) Corresponding PDF fitting results.Figure S7 Rietveld refinement and PDF fitting results for PtCo catalysts annealed at 700°C for different durations followed by acid treatment. (left) Total scattering patterns refined by the Rietveld method. Each partial contribution of the phases determined in Figure 4 of the main text, along with their hkl indices shown as vertical ticks, are displayed. (right) Corresponding PDF fitting results.Figure S8 Phase fraction (wt%) obtained by the PDF fitting. The PtCo samples are annealed at different temperatures for (a) 2h, (b) 10 h, and (c) 20h, followed by acid treatment. Each contribution of the phases determined in Figure 4 of the main textFigure S9 Domain size of PtCo catalysts as a function of annealing temperature. All samples were annealed for (a) 2h, (b) 10 h, and (c) 20h and subsequently treated with acid. Each contribution of the phases determined in Figure 4 of the main textFigure S10 Lattice parameters of PtCo catalysts as a function of annealing temperature and time, as determined by PDF analysis. Each contribution of the phases determined in Figure 4 of the main text. The tetragonal phase (ii) is represented in a cubic lattice for clarity. The error bars represent the estimated standard deviations from the PDF analysis. All samples were annealed for (a) 2h, (b) 10 h, and (c) 20h and subsequently treated with acid.Figure S11 Shortest nearest-neighbor Pt-Pt distances in PtCo catalysts as a function of annealing temperature. All samples were annealed for (a) 2h, (b) 10 h, and (c) 20h and subsequently treated with acid. Each contribution of the phases determined in Figure 4 of the main text.Figure S12 Rietveld refinement and PDF fitting results for PtCo catalysts annealed at 350°C for 2 h without acid treatment. (a) Total scattering pattern refined by the Rietveld method. Each partial contribution of the phases determined in Figure 4 of the main text, along with their hkl indices shown as vertical ticks, are displayed. (b) Enlarged view of the low-angle region of the total scattering pattern. (c) Corresponding PDF fitting result.Figure S13 Rietveld refinement and PDF fitting results for PtCo catalysts annealed at 700°C for 20 h with and without acid treatment. (a, b) Total scattering patterns refined by the Rietveld method for the samples (a) without and (b) with acid treatment. Each partial contribution of the phases determined in Figure 4 of the main text, along with their hkl indices shown as vertical ticks, are displayed. (c, d) Corresponding PDF fitting results for the samples (c) without and (d) with acid treatment. Figure S14. (a) The ECSA, of various catalysts treated at different thermal conditions, (b) Schematic illustration of the temperature gap between the onset of particle growth and the formation of the ordered phase in PtCo catalysts. The red arrow indicates the temperature (350°C) at which particle growth and changes in electrochemical properties are observed. The green arrow indicates the temperature (450°C) at which the ordered phase is detected by XRD and PDF analyses. The blue shaded region represents the temperature range where local structural changes, such as surface ordering or strain, may occur.Figure S15. Mass activity at 0.9 V for the catalysts treated at different thermal conditions.Figure S16. CVs curves for the (a) PtCo-700°C-10h-A and (b) PtCo-350°C-10h-A after various ADT cycles.Figure S17. LSV curves for (a) PtCo-700°C-10h-A and (b) PtCo-350°C-10h-A catalysts before and after ADT cycles.Figure S18. Bar diagram showing the mass activity for (a) PtCo-700°C-10h-A and (b) PtCo-350°C-10h-A catalysts before and after ADT cycles.Figure S19. Electrochemical CO stripping measurement for PtCo-350°C-10h-A for (a) initial state, (b) after 10000 ADT cycles, and (c) after 20000 ADT cycles.Figure S20. Electrochemical CO stripping measurement for PtCo-700°C-10h-A for (a) initial state, (b) after 10000 ADT cycles, and (c) after 20000 ADT cycles.Figure S21. operando HERFD-Pt L3-edge XAS analysis for PtCo-350°C-10h.Figure S22. operando Pt L3-edge XANES spectra at various polarization potentials for (a) PtCo-700°C-10h-A and (b) PtCo-350°C-10h-A catalysts.Table S1. Chemical composition of PtCo alloy catalysts after acid treatment determined by ICP.  Pt wt% Pt at% Co at% PtCo-350°C-2h-A 13.11 81 19 PtCo-350°C-10h-A 13.24 79 21 PtCo-350°C-20h-A 13.34 77 23 PtCo-450°C-2h-A 13.58 71 29 PtCo-450°C-10h-A 13.92 73 27 PtCo-450°C-20h-A 13.28 67 33 PtCo-600°C-2h-A 14.16 66 34 PtCo-600°C-10h-A 14.3 63 37 PtCo-600°C-20h-A 15.06 60 40 PtCo-700°C-2h-A 14.21 66 34 PtCo-700°C-10h-A 14.54 63 37 PtCo-700°C-20h-A 13.58 63 37 PtCo-250°C-2h-A 12.46 95 5 PtCo-300°C-2h-A 13.43 87 13Table S2. Summary of ex-situ EXAFS results of the catalysts for the Pt L3-edge.  Path d/Å CN ΔE0 R/Å σ2/ Å2 R PtCo-350°C-2h-A Pt-Pt 2.712 5.3 5.983 2.726(5) 0.005 1.9%  Pt-Co 2.712 2.3 6.206 2.632(26) 0.006  PtCo-350°C-10h-A Pt-Pt 2.712 5.8 6.454 2.726(5) 0.006 2.0%  Pt-Co 2.712 2.6 7.225 2.631(25) 0.009  PtCo-350°C-20h-A Pt-Pt 2.712 5.3 5.934 2.721(5) 0.007 4.8%  Pt-Co 2.712 2.6 10.793 2.659(45) 0.014  PtCo-450°C-2h-A Pt-Pt 2.691 4.5 5.567 2.703(7) 0.007 1.8%  Pt-Co 2.648 2.1 11.314 2.658(26) 0.009  PtCo-450°C-10h-A Pt-Pt 2.691 4.1 6.247 2.711(5) 0.006 1.6%  Pt-Co 2.648 2.4 9.899 2.672(29) 0.009  PtCo-450°C-20h-A Pt-Pt 2.691 4.7 5.137 2.695(7) 0.006 1.7%  Pt-Co 2.648 3.5 8.871 2.638(15) 0.009  PtCo-600°C-2h-A Pt-Pt 2.691 4.8 6.814 2.703(2) 0.005 0.2%  Pt-Co 2.648 2.8 9.593 2.653(5) 0.007  PtCo-600°C-10h-A Pt-Pt 2.691 4.9 5.908 2.692(3) 0.005 0.4%  Pt-Co 2.648 3.8 8.764 2.643(6) 0.007  PtCo-600°C-20h-A Pt-Pt 2.691 4.8 5.423 2.684(4) 0.005 0.5%  Pt-Co 2.648 3.8 8.856 2.639(7) 0.006  PtCo-700°C-2h-A Pt-Pt 2.691 4.1 7.246 2.695(5) 0.005 1.2%  Pt-Co 2.648 4.0 11.581 2.657(13) 0.006  PtCo-700°C-10h-A Pt-Pt 2.691 4.4 6.455 2.694(3) 0.004 0.4%  Pt-Co 2.648 4.2 8.544 2.646(6) 0.006  PtCo-700°C-20h-A Pt-Pt 2.691 4.8 5.259 2.685(5) 0.005 0.8%  Pt-Co 2.648 4.1 8.572 2.642(9) 0.007   fixed at 0.9, where the  is less than 0.5,  is less than 0.01 from the least-squares fits by ARTEMISTable S3. Summary of ex-situ EXAFS results of the catalysts for the Co K-edge.  Path d/Å CN ΔE0 R/Å σ2/ Å2 R PtCo-350°C-2h-A Co-Pt 2.711 9.4(5) -11.750 2.632 0.009 1.2%  Co-Co 2.711 2.6(5)  -17.169 2.542(20) 0.009  PtCo-350°C-10h-A Co-Pt 2.711 9.2(5) -10.539 2.632(26) 0.009 1.7%  Co-Co 2.711 2.8(5)  -11.321 2.553(21) 0.009  PtCo-350°C-20h-A Co-Pt 2.711 9.1(5) -10.965 2.659 0.009 1.1%  Co-Co 2.711 2.9(5)  -11.550 2.540(17) 0.009  PtCo-450°C-2h-A Co-Pt 2.648 7.9(5) -2.237 2.658 0.009 1.8%  Co-Co 2.691 4.1(5)  -4.524 2.600(20) 0.007  PtCo-450°C-10h-A Co-Pt 2.648 7.2(5) -5.118 2.672 0.008 0.7%  Co-Co 2.691 4.8(5)  8.622 2.737(29) 0.016  PtCo-450°C-20h-A Co-Pt 2.648 7.1(5) -4.207 2.638 0.006 2.0%  Co-Co 2.691 4.9(5)  9.983 2.743(29) 0.016  PtCo-600°C-2h-A Co-Pt 2.648 7.1(5) -3.629 2.653 0.006 1.7%  Co-Co 2.691 4.9(5)  9.964 2.754(32) 0.014  PtCo-600°C-10h-A Co-Pt 2.648 6.5(5) -3.318 2.643 0.006 1.5%  Co-Co 2.691 5.5(5)  6.744 2.721(2) 0.011  PtCo-600°C-20h-A Co-Pt 2.648 6.4(5) -3.318 2.639 0.005 1.3%  Co-Co 2.691 5.6(5)  6.744 2.749(22) 0.015  PtCo-700°C-2h-A Co-Pt 2.648 6.5(5) -4.235 2.647 0.005 1.3%  Co-Co 2.691 5.5(5)  8.319 2.739(12) 0.015  PtCo-700°C-10h-A Co-Pt 2.648 4.8(5) -4.168 2.646 0.004 1.0%  Co-Co 2.691 7.2(5)  3.321 2.686(9) 0.009  PtCo-700°C-20h-A Co-Pt 2.648 4.8(5) -4.634 2.642 0.004 1.2%  Co-Co 2.691 7.2(5)  3.512 2.686(12) 0.009   fixed at 0.9, where the  is less than 0.5,  is less than 0.01 from the least-squares fits by ARTEMISTable S4. Phase fraction of PtCo catalysts annealed at 700°C for 20 h with and without acid treatment.  Phase (ii) Phase (iii) Phase (iv) Phase (v) After acid treatment 21.107 16.061 30.206 32.626 Before acid treatment 21.064 17.798 33.913 27.225Table S5. Lattice parameters of PtCo catalysts annealed at 700°C for 20 h before and after acid treatment.  Phase (ii) Phase (iii) Phase (iv) Phase (v)  c /Å a /Å c /Å a /Å a /Å a /Å After acid treatment 3.69686 2.68477 3.83027 2.67418 3.87509 3.92309 Before acid treatment 3.69459 2.68625 3.82087 2.64118 3.83811 3.89098Note that We set the upper limit of the pFCC-Pt lattice parameter to be 3.9231Å, which is the one for pure Pt.Table S6. Domain sizes of PtCo catalysts annealed at 700°C for 20 h with and without acid treatment.  Phase (ii) Phase (iii) Phase (iv) Phase (v) After acid treatment 57.29664 16.94926 14.2217 4.93004 Before acid treatment 56.33593 23.54757 12.25646 13.09178S2image4.pngimage5.pngimage6.pngimage7.pngimage8.pngimage9.pngimage10.pngimage11.pngimage12.pngimage13.pngimage14.pngimage15.pngimage16.pngimage17.pngimage18.pngimage19.pngimage20.pngimage21.pngimage22.pngimage23.pngimage1.pngimage2.pngimage3.png